Harder than you would think given the obvious and physical nature of your injury. Even with something like this, they want piles and piles of documentation, and if you've been in school since then, they'll want to see that you got accommodations in school. They may also balk at seemingly random things, e.g., if your grades are relatively high after the injury and with accommodations, they may make the (obviously logically invalid) argument that you don't need the accommodations because you're doing well.

It can be done, but be ready for a fight.

(The only reason I know about this is that I had a student who did it.)